Condensate recovery in oxidation of alkyl benzenes



United States Patent Ofiice 3,047,614 1 CONDENSATE RECOVERY IN OXIDATION OF ALKYL BENZENES Robert E. Pennington and James K. Nickerson, Baytown,

Tex., assignors, by mesne assignments, to, Esso Research and Engineering Company, Elizabeth, N.J., a corporation of Delaware Filed July 5, 1960, Ser. No. 40,775

8 Claims. (Cl. 260475) sequence, unless special precautions are taken, it will not be possible to obtain dependable phase separation of the effluent into an off-gas fraction, an aqueous fraction and an alkyl benzene condensate fraction.

In the oxidation-esterification reaction it has been found to be necessary to remove at least a major portion of the water that is formed during the reaction so that the reaction mixture will contain, for example, not more than about 5 weight percent of water. This is conveniently accomplished by conducting the reaction at a temperature whichis near the boiling point of Water for the pressure employed. However, volatilization of the water will also result in volatilization of other components of the reaction mixture to a significant extent whereby unreacted methanol, methanol oxidation products, unreacted alkyl benzene and alkyl benzene conversion products are vaporized and leave the reaction zone together with the volatilizedwater and ofi gas components (e.g., nitrogen, carbon monoxide, carbon dioxide). Because of'the comparatively large quantity of unreacted or partially reacted material present in the vapor, it is desirable to process this vapor for the recovery of valuable components thereof. It has been discovered, however, that this presents serious problems, particularly where recycle type operations are employed.

When the vapor from the reaction zone is cooled to a temperature sufficient to liquefy the condensable components thereof, the thus-obtained condensate will comprise a mixture of water, methanol, methanol oxidation products, alkyl benzene and alkyl benzene conversion products. It might ordinarily be expected that the methanol, methanol oxidation products and water would separate from the alkyl benzene and alkyl benzene conversion products in order to provide a heavy aqueous phase which could be separated from the alkyl benzene condensate phase by any suitable phase separation technique such as gravity settling. However, the presence of large quantities of methanol in the aqueous phase tends to decrease the specific gravityof the aqueous phase, Whereas the concentration of alkyl benzene conversion products in the alkyl benzene phase tends to increase the specific gravity of the alkyl benzene condensate phase. Thus, the normal specific gravity differential that exists with respect to water than the aqueous phase. This will result in phase inversion. In an intermediate situation, concentrations of the various components present may be such that the condensate will comprise a single phase containing both the alkyl benzene and water components in contrast to the separate water and oil phases that would normally be expected or else the water phase and oil phase will have approximately equal specific gravities and will not separate. Still further, the changes in composition required to bring about the above-noted changes in the specific gravity relationship are slight so that even minor changes in the composition of the condensate will result in major changes in the observed settling rates thereof. As a concondensate with a supernatant alkyl benzene condensate phase during continuous operations.

It has been found that the vapor from a reaction zone wherein an alkyl benzene is catalytically oxidized with molecular oxygen in the presence of methanol may be cooled to liquefy condensable components therein, and the condensed liquids may be separated from the off-gas and resolved into an aqueous fraction and an alkyl benzene off-gas condensate fraction in the presence of additional quantities of water over and above the amount of water normally present in the vapor. Thus, phase separation may be obtained in dependable fashion by adding by distillation) to obtain the methanol contained therein for recycle. Methanol oxidation products may also be recovered. The remainder of the aqueous phase may be rejected, even though it has some unreacted alkyl benzene and alkyl benzene conversion products dissolved therein.

This is a practical means of operation, but certain problems still exist in connection with the water stream for rejection. This is related to the fact that a certain amount of the aromatic feed stock and its derivatives remain dissolved or entrained or both in the aqueous phase and are not returned to the reaction zone with the oil phase. In the distillation column, the major portion of the aromatic feed. stock is surprisingly carried overhead with the methanol and in this way may find its way back to the reactor. This is not the case with the aromatic oxidationesterification derivatives which are considerably higher in boiling point. These materials appear in the bottoms stream and unless some recovery means are adopted, will be lost with the discarded water.

This loss may be somewhat minimized by operating in i a manner wherein the injection water is drawn from the distillation column bottoms with no fresh water. introduced. Thus, the volume of the aqueous stream discarded is reduced to only the water of reaction originally present in the condensate from the reactor 01f gases.

The losses of desirable materials may be further reduced by the following procedures of the present invention. In accordance with this procedure, the aqueous bottoms are contacted in a mixing zone with the oil layer from the phase separation zone. After being settled, these materials are decanted with the oil layer now being returned to the reactor, part of the water being used as injection water to bring on the initial phase separation, and excess water being rejected from this zone. As an alternate, fresh injection water may be used and all the aqueous phase from the second decanter rejected from the system.

The alkyl benzene feed stock to be used in accordancewith the present invention is an alkyl benzene containing one or a plurality of C to C alkyl groups attached direct- Patented July 31, 1962 1y to the benzene ring. By way of example, the starting materials may comprise methyl benzenes such as toluene, xylenes, trimethyl benzenes, tetramethyl benzenes, pentamethyl benzene or hexamethyl benzene or a corresponding ethyl, n-propyl, isopropyl, butyl, or isobutyl benzene. Polyalkyl benzenes containing a plurality of alkyl groups of varying chain lengths may also be utilized such as, for example, a cymene, 1-methyl-3-butyl benzene, l-methyl- 4-tertiary-butyl benzene, etc. A single isomer, a plurality of isomers or a plurality of alkyl benzenes of different molecular weight may be utilized.

The alcohol feed material is methanol.

The preferred starting materials are the methyl benzenes and methanol, because less oxygen is required, because less by-product water is formed, and because workup of the reaction mixture is simplified.

The oxidizing medium to be employed is molecular oxygen and a preferred oxygen charge stream is air. However, it is within the scope of the present invention to utilize purified molecular oxygen or molecular oxygen diluted with another inert gas such as carbon dioxide.

The catalyst that is used is a salt of a polyvalent heavy metal which is soluble in the liquid reaction mixture as exemplified by the salts (e.g., the naphthenates, acetates, bromides, etc.) of cobalt and manganese, etc. The catalyst concentration should preferably be within the range from about 1 to about 10,000 ppm. of soluble polyvalent heavy metal based on the total weight of the reaction mixture. Catalyst promoters are optionally employed and, more particularly, soluble bromine salts such as cobalt bromide, ammonium bromide, manganese bromide, etc. or hydrobromic acid are employed because of their high promotional activity, both with respect to the oxidation reactions and with respect to the esterification reactions that are involved.

The term recycle type operation as used in this application means a continuous operation wherein products of the conversion operation (both liquid and vapor) are continually processed exteriorly of the reaction zone for the removal of nonreactive components of the reaction mixture and wherein unreacted alcohol, unreacted alkyl benzenes and alkyl benzene conversion products are returned to the reaction zone.

The term alkyl benzene conversion products as used herein is intended to include those aromatic type reaction products that are formed in the reaction zone including the reaction products of alkyl benzene with the oxygen only, as well as the reaction products (such as oxidationesterification) of alkyl benzene, oxygen and methanol. Also, since the alkyl benzene will ordinarily contain small quantities of aromatic type impurities, the term alkyl benzene conversion products is also intended to include conversion products of the aromatic impurities. Accordingly, for the purpose of this application, the term alkyl benzene conversion products is defined as the aromatic conversion products of the alkyl benzene feed stock and aromatic impurities contained therein and comprising aromatic alcohols, aromatic aldehydes, aromatic acids, methyl esters of aromatic acids, partial methyl esters of polybasic aromatic acids, etc.

The term methanol oxidation products as used herein means reaction products of methanol and oxygen including formaldehyde, formic acid, methyl formate and methylal.

The invention will be further illustrated with respect to the accompanying drawing wherein:

The sole FIGURE isa schematic flow sheet illustrating one embodiment of the present invention.

Turning now to the drawing, there is schematically disclosed a reactor 2% to which an alkyl benzene, air, and methanol are respectively charged by lines 202, 206, and 210.

A liquid product line 214 containing a pressure reducing valve 216 leads to a flash zone 218, and an off gas line 220 control-led by a valve 222 leads to a cooler 224.

Within the reaction zone 200 the alkyl benzene, the molecular oxygen present in the air, and the methanol are catalytically reacted in liquid phase under suitable operating conditions including, for example, a temperature within the range of about 350 to 550 F. a residence time in the range of about 0.2 to 2 hours, and a pressure within the range of about 500 to 1000 p.s.i.g. such that at least about 1 weight percent of methanol (and preferably l to 15 weight percent) is present in the liquid reaction mixture. Any suitable polyvalent metal salt which is soluble in the reaction mixture may be used as the catalyst, as exemplified by the acetates, naphthenates, formates, etc., of cobalt, manganese, etc. The catalyst may be added by way of a catalyst charge line 18 controlled by a valve 20.

For purposes of description, it may be assumed that the alkyl benzene is a xylene. It will be understood, however, that any other suitable alkyl benzene, as described above, could be used.

If the cit gas in line 220 contains an excessive amount of the heavier xylene conversion components (e.g., methyl toluates, monomethyl phthalates, dimethyl phthalates, etc.) valve 222 is closed and the off gas is passed by a branch line 226 controlled by valve 228 to a precooler 230 wherein the vapors are cooled to a temperature, for the pressure employed, sufficient to substantially selectively liquefy only the heavier xylene conversion products such as the methyl toluates, monomethyl phthalates and dimethyl phthalates. This procedure will be employed particularly in situations wherein the xylene type components of the off-gas contain in excess of more than about 30' weight percent of the heavy xylene conversion products in the condensate. From precooler 230, the partially condensed material is charged by Way of a line 232 to a drum 234 wherein the condensed heavy Xylene partial conversion products are separated from the remainder of the vapor. The heavy xylene partial conversion product may be withdrawn by way of a line 236 leading back to liquid product line 214.

Within the cooler 224 the remaining portion of the condensable cit-gas, is cooled to a temperature, for the pressure employed, suflicient to liquefy the condensable components of the vapor of the line 220. The resultant ofi gas condensate stream is passed by way of a line 250 to a drum 252 wherein the tail gas is withdrawn by way of a vent line 254. The condensate is discharged from drum 252 by way of a line 256 containing a pressure reducing valve 258 leading to a separator 262. Water is added to the condensate in any desired manner such as, for example, by way of a water charge line 263 controlled by a valve leading tothe line 256. Within the separator 262 the condensate and added water are resolved into a lower aqueous phase comprised principally of water, methanol and methanol oxidation products which are discharged by way of a line 264 for further processing and a supernatant xylene phase which is discharged by way of a line 269.

The aqueous phase is charged by way of line 264 to a suitable distillation zone illustrated schematically in the drawing as a single distillation column 106 wherein the aqueous stream 264 is separated into a light overheads fraction 108 composed principally of methanol and methanol oxidation products (and also containing some water and unreacted xylenes feed stock) and a bottoms water fraction 110 composed principally of water and containing some xylene conversion products.

It is generally desirable to recover methanol from the overheads fraction 108 for recycle although it may be discarded from the system by way of a discard line 112 controlled by a valve 114. Thus, the overheads 108 may suitably be charged to a second distillation column 116 where it is separated into an overheads fraction 118 composed of methanol and methanol oxidation products and abottoms fraction 120 composed principally of methanol and containing some unreacted xylenes. The bottoms fraction 120 is preferably recycled to the reaction zone 200 by way of a suitable recycle line (not shown) in order to supply at least a portion of the methanol requirements for the system.

The water fraction- 110 from the distillation column 106 is charged by way of a branch line 122 to a suitable mixing device such as a baflie plate incorporator 124. It is generally desirable to charge substantially all of the bottoms fraction 110 to the mixer 124 although, if desired, a portion of the water may be purged from the system by way of a purge line 126 controlled by a valve 128.

The supernatant xylene phase 269 from the separator 262 is also charged to the mixer '124 and the two streams, after being thoroughly commingled, are discharged by way of a line 130 leading to a separation zone 132 wherein phase separation is accomplished. The supernatant xylene phase containing a major amount of the xylene conversion products initially present in the Water fi'action'110 is withdrawn by way of a recycle line 134 which suitably leads to the alkyl benzene charge line 202.

The water fraction is discharged from separator 132 by way of a line 136 controlled by a valve 137. All of the water may be discarded from the system by way of line 136. Preferably, however, at least a portion of the water in line 136 is routed by way of a branch line 138 controlled by a valve 140 leading to the water charge line 263.

As the result of this operation, a significant portion of the xylene conversion products that would normally be lost from the system by water fraction 110 are recovered by way of a recycle stream 134, thereby improving the selectivity'of the process and-thereby abating a potential pollution problem.

The liquid product stream withdrawn by line 214 (containing pressure reduction valve 216) from the reactor 200 will comprise not only dicarbomethoxy benzene, unreacted xylene and xylene conversion products, but also free methanol, methanol oxidation products and, normally, at least a minor amount of water.

In order to facilitate the processing of the liquid product stream 214, it is desirable in many instances to separate the stream 214 into a heavy fraction containing a heavy oxidate stream containing a concentrated amount of dicarbomethoxy benzene and a lighter fraction substantially free from the dicarbomethoxy benzene and other dibasic materials.

The initial separation may conveniently be accomplished in the flash zone 218 wherein the flashing conditions are adjusted so as to vaporize a substantial amount of the unreacted xylene and substantially all of the water, unreacted methanol and methanol oxidation products overhead as flashed liquid product by way of a line 266 leading to a condenser 270. In this situation, the heavy oxidate is discharged by Way of a line 272 for further processing. Suitable means such as trays 102 at the top of zone 218 may be provided in order to prevent excessive carryover of heavy oxidate into line 266.

Difiiculties will be encountered in processing the vaporized reaction product in the line 266 because of the specific gravity problem. 1

Within the cooler 270 the condensable components are liquefied, and the resultant flashed liquid product condensate stream is then charged by way of a line 288 to a manifold 104.

From manifold 104 the condensate is preferably routed by way of a branch line 142 controlled by a valve 143 to the charge line 256 for the separator 262 in order to improve the efliciency of the process by processing the condensate 288 in admixture with the ofi gas condensate 256. However, the condensate 288 may be separately processed, if desired. Thus, for example, the condensate may be routed from manifold 104 by way of a line 144 controlled by a valve 146 to a phase separator 148. Water will also be added to the line 144 by way of a water charge line 150 con-trolled by a valve 152 in order to insure positive phase separation.

The oil from separator 148 may be withdrawn by way of a line controlled by valve 92 for recycle to the reaction zone zoo. Alternately, it may be charged by Way of the line 154 controlled by a valve 156 to a suitable mixing device such as a baffle plate incorporator 158 for a purpose to be described.

The water phase from separator 148 may be discharged by way of a line 160 controlled by a valve 162 leading to charge line 264 which feeds into distillation column 11-06 in order to recover xylenes and xylene conversion products contained therein. Alternately, the water phase may be charged by way of a branch line 164 controlled by valve 166 to a distillation zone illustrated schematically in the drawing as a single fractionator 168 wherein the water fraction may be separated into an overhead methanol oxidation fraction 170, a methanol distillate fraction 172 (containing unreacted xylenes) and a bottoms water fraction discharged by way of a line 174 controlled by a valve 176 and containing dissolved xylene oxidation products. Although the water fraction to the distillation column 106. Alternately, the water.

fraction 174 may be charged by Way of a branch line 182 controlled by a valve 184 to the baffle plate incorporator 158 wherein it is brought into intermediate contact with the oil phase 154. The resultant mixture is discharged from incorporator 158 by way of a line 186 to a separator 188 wherein phase separation occurs. oil phase is withdrawn by way of a line 190 for recycle to the reactor 200. The water phase is discharged by way of a line 192 controlled by a valve 194. If desired, a portion of the water in the line 192 may be charged by way of a recycle line 196 controlled by a valve 198 to the water charge line for the line 144.

It will be understood that modifications of the process shown in the drawing may be made and that the process shown in the drawing is by way of illustration only. For example, all or a portion of the fresh alkyl benzene feed stock may be charged to the process by way of a line 400 controlled by a valve 402 leading to the charge line 256 for the separator 262 in order to improve the phase separation to be accomplished in the zone 262. Similarly, all or a portion of fresh alkyl benzene feed stock could be charged by way of a line 404, controlled by a valve 406 leading to the charge line 144 for the separator 148 in order to promote phase separation in the separator 148.

It will also be understood that the water to be added to the charge streams to the separators 148 and 262 may be added directly to the separators by suitable lines (not shown) or at any other upstream point from the separator 262 and downstream from reaction zone 200 and flash zone 218.

The invention will be further illustrated by the following specific examples which are given by way of illustration and not as limitations on the scope of this invention. Where parts are given, they are parts by weight.

EXAMPLE I zone 200 through the line 202, the fresh xylene containing an amount of cobalt naphthenate sufiicient to provide about 5 parts per million of dissolved cobalt in the liquid phase. Charge air at the rate of about 0.4 part per part of p-xylene. After initiation of the oxidation reaction,

The supernatant charge methanol by way of line 210 in the ratio of about 0.4 part of methanol per part of p-xylene. Start recycle operations in the manner shown schematically in the drawing.

Thus, process an off gas stream after removal through the oif gas line 229 by cooling in the cooler 224 in order to condense liquefiable components followed by separation of the tail gas from the condensate in drum 252. Charge the condensate by way of line 256 to a separator 262 and add about 25 weight percent of Water to the condensate by way of a line 263.

Within the separator 252 the condensate resolves by gravity separation into a supernatant xylene condensate phase 269 in which is charged to mixer 124 and an aqueous fraction 264 which was fractionated in a distillation zone 106 for the recovery of methanol. Methanol recovered by line 120 is recycled to the reaction zone 2.09. Water from the line 110 is charged to mixer 124.

The oil phase and water phase after being thoroughly commingled in mixer 124 is passed through line 130 to separator 132 and separated therein into an oil phase and an aqueous phase. In a representative run conducted in this fashion, the compositions for the fractions 110, 269, 134 and 136 were found by analysis to be those set forth in Table I.

Table I STREAM ANALYSES (110) (269) (134) (136) Column Oil From Oil From Aqueous Bottoms, First Second From Component Wt. per- Decant, Decant, Second cent Wt. per- Wt. per- Decant,

cent cent Wt. percent Dimethylterephthalate 0. 4 5. 2 5. 9 0. Monomethyltcrephthalate. 0. 1 0. 4 1. 1 0. 1 Methyl p-Toluate 1. 9 23. 6 27. 7 0. 2 p-Toluic Acid 0. 6 2. 4 3. 3 0. 3 p-Tolualdehyde 0.2 1. 4 1. 1 0. 0 p Tolyl Alcohol 0. 1 0. 4 0. 3 0.1 0.2 53. 7 56. 7 0.0 0. 6 3. l 1. 8 1. 6 0.0 0.0 0.0 0.3 0.0 3. 9 2. 1 1. 1 0.0 0. 1 0. 0 0. 6 0. 0 0. 0. 0 0. 0 18. 9 4. 4 0.0 17. 2 1. 3 0. 1 0.0 1. 5 75. 5 0. 8 0.0 77. 5

From Table I it can be calculated that 80 percent of the aromatic materials in the fraction 110 were recovered as a part of the second oil fraction 134.

EXAMPLE II By way of contrast, it was attempted to recover the aromatic materials from the line 110 by a stream stripping-azeotropic technique. Thus, a sample of the material in the line 110 was refluxed in a well stirred one liter round bottom flask fitted with a condenser and a decanting leg on the reflux return. At the outset, an oil layer was obtained which floated on the water layer. This material was withdrawn and after further refluxing a new oil layer formed which sank below the water layer. Thus, the phase separation obtained would be undependable for continuous operations. To further demonstrate the limitations of this technique, vigorous refluxing was maintained for a period of about four hours and then after cooling, the oil phase from the reflux vessel (which separates from the water when cooled) and the oil layer from the decanter were weighed. Only about 40 percent of the oil material had been stripped overhead.

What is claimed is:

1. In a continuous method for the production of a carbomethoxy benzene by the catalytic liquid phase oxidation of a C to C alkyl benzene in a reaction zone with molecular oxygen in the presence of methanol and wherein reaction products, including an off gas stream and a liquid product stream, are continuously withdrawn from said reaction zone, said off gas stream and said liquid reaction mixture stream comprising normally liquid components including Water of reaction, unreacted methanol, methanol oxidation products, unreacted alkyl benzene, and alkyl benzene conversion products, and wherein at least a portion of said reaction products are recovered as a condensate fraction comprising water of reaction, unreacted methanol, methanol oxidation products, unreacted alkyl benzene and alkyl benzene conversion products, by continuously charging said condensate fraction to a first separation zone, continuously charging additional Water to said separation zone in an amount suflicient to cause separation of said condensate fraction and said added water into a lower phase comprising water, methanol and methanol oxidation products and a supernatant phase comprising unreacted alkyl benzene and alkyl benzene conversion products, the improvement which comprises fractionating said lower water phase into a heavy water fraction and a light overhead fraction comprising methanol and methanol oxidation products, continuously admixing said heavy water fraction with said supernatant phase in a second separation zone wherein there is formed an alkyl benzene phase comprising unreacted alkyl benzene and alkyl benzene conversion products and a water phase substantially free of alkyl benzene conversion prodnets, and recycling said alkyl benzene phase to said reaction zone.

2. A method as in claim 1 wherein said condensate fraction is recovered from said off gas stream.

3. A method as in claim 2 wherein at least a portion of said water phase is contacted with said condensate fraction.

4. In a continuous method for the production of a dimethyl phthalate by the catalytic liquid phase oxidation of a xylene in a reaction zone with molecular oxygen in the presence of methanol under reaction conditions including a temperature within the range of about 350 to about 550 F. and a pressure within the range of about 500 to about 1000 p.s.i.g. and wherein reaction product streams, including an ofi gas stream and a liquid product stream, are continuously withdrawn from said reaction zone, said off gas stream and said liquid product stream comprising normally liquid components including water of reaction, unreacted methanol, methanol oxidation products, unreacted xylene and xylene conversion products, methyl toluate and heavier xylene conversion products, wherein first condensate from said oil gas is recovered which comprises said normally liquid components, at least a portion of said methyl toluate and heavier xylene conversion products are removed from said first condensate to provide a first condensate fraction, said liquid product stream is separated into a heavy liquid fraction containing said dimethyl phthalate and a vapor fraction comprising said normally liquid components including methyl toluate and heavier xylene conversion products, said dimethyl phthalate is continuously recovered from said heavy liquid fraction and the remainder of said heavy liquid fraction is recycled to said reaction zone, said vapor fraction is condensed to provide a second condensate, at least a portion of said methyl toluate and heavier xylene products are removed from said second condensate to provide a second condensate fraction, and wherein from about 5 to 50 weight percent of additional water is added to said first and second condensates, the improvement which comprises admixing said first condensate fraction and said second condensate fraction before adding said water, separating said admixture after adding said water into a water phase containing unreacted methanol and methanol oxidation products and a supernatant xylene phase comprising unreacted xylene and xylene conversion products, fractionating said lower water phase into a Water fraction containing xylene conversion products and a methanol fraction comprising methanol and methanol oxidation products, continuously mixing said water fraction with said supernatant xylene phase,

charging said mixture to a second separation zone, separating said mixture into said supernatant xylene phase and said water fraction, and recycling said xylene phase to said reaction zone.

5. A method in accordance with claim 1 wherein the alkyl benzene is a methyl benzene.

6. In a continuous method of producing a dirnethyl phthalate by the catalytic liquid phase reaction of a xylene in a reaction Zone with molecular oxygen and methanol under conditions including a temperature within the range of about 350 F. to about 550 F. and a pressure within the range of about 500 p.s.i.g. to about 1000 p.s.i.g., wherein reaction products including an off gas condensate staream and a flashed liquid product condensate stream are continuously recovered from said reaction zone, and wherein water is admixed with at least one of said condensate streams whereby said admixed stream is separated into a supernatant xylene phase and a lower aqueous phase, the improvement which comprises fractionating said lower aqueous phase into a water fraction containing xylene conversion products and a methanol fraction, contacting said water fraction with said supernatant xylene phase whereby said xylene conversion products are removed from said water, and recycling said supernatant xylene phase to said reaction zone.

7. A method in accordance with claim 6 wherein the water admixed with said condensate stream amounts to about 5 to about 50 weight percent of said condensate.

8. In a process of recovering a condensate stream from the oxidation-esterification reaction between a methyl benzene, molecular oxygen, and methanol, wherein said condensate stream comprises unreacted methanol, unreacted methyl benzene, methyl benzene conversion products, methanol conversion products and water of reaction, and wherein water in amounts from about 5% to about 50% by weight based on said condensate stream is added to said stream whereby a methyl benzene supernatant phase and a methanol containing lower aqueous phase are formed, said aqueous phase containing at least a portion of said methyl benzene conversion products, the improvement which comprises fractionating said aqueous phase to remove methanol therefrom and contacting said fractionated aqueous phase v with said supernatant phase whereby said methyl benzene conversion products are ab- 20 sorbed by said supernatant phase.

2,879,289 Johnson Mar. 24, 1959 

1. IN A CONTINUOUS METHOD FOR THE PRODUCTION OF A CARBOMETHOXY BENZENE BY THE CATALYTIC LIQUID PHASE OXIDATION OF A C1 TO C4 ALKYL BENZENE IN A REACTION ZONE WITH MOLECULAR OXYGEN IN THE PRESENCE OF METHANOL AND WHEREIN REACTION PRODUCTS, INCLUDING AN OFF GAS STREAM AND A LIQUID PRODUCT STREAM, ARE CONTINUOUSLY WITHDRAWN FROM SAID REACTION ZONE, SAID OFF GAS STREAM AND SAID LIQUID REACTION MIXTURE STREAM COMPRISING NORMALLY LIQUID COMPONENTS INCLUDING WATER OF REACTION, UNREACTED METHANOL, METHANOL OXIDATION PRODUCTS, UNREACTED ALKYL BENZENE, AND ALKYL BENZENE CONVERSION PRODUCTS, AND WHEREIN AT LEAST A PORTION OF SAID REACTION PRODUCTS ARE RECOVERED AS A CONDENSATE FRACTION COMPRISING WATER OF REACTION, UNREACTED METHANOL, METHANOL OXIDATION PRODUCTS, UNREACTED ALKYL BENZENE AND ALKYL BENZENE CONVERSION PRODUCTS, BY CONTINUOUSLY CHARGING SAID CONDENSATE FRACTION TO A FIRST SEPARATION ZONE, CONTINUOUSLY CHARGING ADDITIONAL WATER TO SAID SEPARATION ZONE IN AN AMOUNT SUFFICIENT TO CAUSE SEPARATION OF SAID CONDENSATE FRACTION AND SAID ADDED WATER INTO A LOWER PHASE COMPRISING WATER, METHANOL AND METHANOL OXIDATION PRODUCTS AND A SUPERNATANT PHASE COMPRISING UNREACTED ALKYL BENZENE AND ALKYL BENZENE CONVERSION PRODUCTS, THE IMPROVEMENT WHICH COMPRISES FRACTIONING SAID LOWER WATER PHASE INTO A HEAVY WATER FRACTION AND A LIGHT OVERHEAD FRACTION COMPRISING METHANOL AND METHANOL OXIDATION PRODUCTS, CONTINUOUSLY ADMIXING SAID HEAVY WATER FRACTION WITH SAID SUPERNATANT PHASE IN A SECOND SEPARATION ZONE WHEREIN THERE IS FORMED AN ALKYL BENZENE PHASE COMPRISING UNREACTD ALKYL BENZENE AND ALKYL BENZENE CONVERSION PRODUCTS AND A WATER PHASE SUBSTANTIALLY FREE OF ALKYL BENZENE CONVERSION PRODUCTS, AND RECYCLING SAID ALKYL BENZENE PHASE TO SAID REACTION ZONE. 